class_docstr: Represents a dendrogram, a tree with a specified branching order.  This
  must be initialised with the leaf items, then iteratively call merge for
  each branch. This class constructs a tree representing the order of calls
  to the merge function.
code: def __repr__(self):
      if len(self._items) > 1:
          root = _DendrogramNode(self._merge, *self._items)
      else:
          root = self._items[0]
      leaves = root.leaves(False)
      return "<Dendrogram with %d leaves>" % len(leaves)
  
imports: import copy
  from abc import abstractmethod
  from math import sqrt
  from sys import stdout
  from nltk.cluster.api import ClusterI
label_desc: Use image node_id 5 for calling the Dendrogram obj's underlying member method code with example usage: obj.__repr__() and returns: unknown